1. Field of the Invention
The invention relates to novel oil-soluble methylol polyesters derived from the reaction of a hydrocarbon substituted succinic anhydride or acid and a cyclic poly(methylol) compound. These novel oil-soluble polyesters have utility as additives for oleaginous compositions and systems including fuels, automatic transmission fluids and lubricating oils.
2. Description of the Prior Art
In the operation of a internal combustion engine, there are many "Boundary Lubrication" conditions where two rubbing surfaces must be lubricated, or otherwise protected so as to prevent wear and to insure continued movement. Moreover, where, as in most cases, friction between the two surfaces will increase the power required to effect movement and where the movement is an integral part of an energy conversion system, it is most desirable to effect the lubrication in a manner which will minimize this friction and/or reduce wear. As is also well known, both wear and friction can be reduced, with various degrees of success, through the addition of a suitable additive or combination thereof, to a natural or synthetic lubricant. Similarly, continued movement can be insured, again with varying degrees of success, through the addition of one or more appropriate additives.
While there ae many known lubricant additives which may be classified as antiwear, antifriction and extreme pressure agents and some may in fact satisfy more than one of these functions as well as provide other useful functions, it is also known that many of these additives act in a different physical or chemical manner and often compete with one another, e.g. they may compete for the surface of the moving metal parts which are subjected to lubrication. Accordingly, extreme care must be exercised in the selection of these additives to insure compatibility and effectiveness.
Known ways to solve the problem of energy losses due to high friction in crankcase lubrication include the use of synthetic ester base oils which are expensive, the use of insoluble molybdenum sulfide and graphite dispersions which have the disadvantage of giving the oil composition a black or hazy appearance and the use of lubricants containing dialkyl dithiophosphates (an additive known to provide enhanced antioxidant and antiwear properties to the lubricant) in combination with an ashless dispersant and an ester of a polycarboxylic acid and glycol (see U.S. Pat. No. 4,105,571). The referenced ashless dispersant includes ester containing types derived from alkenylsuccinic anhydride wherein the alkenyl group contains about 50 to about 400 carbon atoms (see col. 6, lines 35-38 of said U.S. Pat. No. 4,105,571) and monohydric and polyhydric alcohols such as cyclohexanol, cyclopentanol, . . ., 2-methylcyclohexanol, . . ., pentaerythritol, trimethylol propane, . . ., etc., (see col. 7, lines 30-64 of said U.S. Pat. No. 4,105,571).
At least two cyclic poly(methylol) compounds are taught in the literature:
2,2,6,6-tetramethylol cyclohexanol is shown in U.S. Pat. No. 2,493,733; and, anhydroenneaheptitol (a/k/a tetrahydro-3,3,5,5-tetrakis (hydroxy methyl)-4-pyranol) is shown in the Encyclopedia of Chemical Technology, Second Edition, by Kirk-Othmer in Vol. 1, page 596 published by Interscience Publishers, New York, New York.